Waveboxes and 4' acrylic 150

[wbeavers]

I have been putting together a new setup, and I am ordering the tank soon. The tank will be made completely of 1/2" cell cast acrylic. It would be 48"x30"x24" tall tank with the rear outside coast to coast overflow w/ 24" of centered teeth. The bracing would be 4" all the way around with a 2" wide center brace. The over flow will also be dropped an inch to allow for wave space. After mentioning that I wanted to use a couple of 6100s & a wavebox the manufacterer said this:

I really don't recommend putting a wave box in a tank that small, that is made out of acrylic. It would beat against the seams and cause stress on the joints. It might start to craze after a while. That might also lead to tank failure. If you were to over build (use 3/4" acrylic) the tank it might be ok, but it might not either. These tanks are not made to handle water movement like that. Its like having a hammer banging up against the sides of the tank. At some point in time it causes fatigue.

Is this tank manufacturer being over cautious? I know you recommed acrylic tanks over glass tanks for wave boxes, but do you have recommendations for tank construction? Should I have the sides upgraded to 3/4"?

 

[rvitko]

First off I have never used an acrylic tank so I can't recommend one over the other but the theoretical is that acrylic tanks when properly assembled are welded and become one fused piece not glued like glass. I have no experience with acrylic what so ever. I think is anology is a bit harsh, comparing a 1" wave (max) to a hammer is not realistic, a more apt anology would be having a 5 year smack the tank with his open hand. Beyond that I cannot say what effects it could have.

 

[ichthyman]

First, if your concerned about crazing and joint strength then a annealing process should be utilized. Any fabrication steps such as cutting, machining, polishing or cementing of acrylic sheet have a tendency to induce internal stresses into the material. These "stresses" diminish the toughness and craze resistance of the material. These properties can be returned to the acrylic by relieving the stress with proper annealing. Annealing is done by through a controlled heating and cooling process. Annealing takes a lot of time and therefore not often done.

Second, the whole tank should be made out of thicker material. IMO at those dimensions, 1/2" material and a Wave Box is asking for trouble. Here is a link to Cyro Plastics . A lot of tank manufacturers use Cyro because it is cheaper. It less expensive because, as you can see from the link, their sheet thicknesses are not true. Cyro's 1/2" material is really only .472 of an inch thick. Even if your manufacturer doesn't use Cyro products the program is still useful as most acrylic sheets have similar tolerances. For tanks with Wave Boxes I generally like to go one size above what is recommended by Cyro's program.

Third, I would avoid solvent cements. Two part polymerizable cement, IPS Weld-on 40, should be used to cement parts together. Solvent joints are faster to prepare and dry which speeds up the fabrication process but they're not as strong. Look at IPS's website for product bulletins and compare the bonding strenghts. You'll notice Weld-on 40, a two part polymerized cement, is what is recomended for aquariums.

Good Luck!

 

[rvitko]

Thanks John!

 

[wbeavers]

Second, the whole tank should be made out of thicker material. IMO at those dimensions, 1/2" material and a Wave Box is asking for trouble. Here is a link to Cyro Plastics . A lot of tank manufacturers use Cyro because it is cheaper. It less expensive because, as you can see from the link, their sheet thicknesses are not true. Cyro's 1/2" material is really only .472 of an inch thick. Even if your manufacturer doesn't use Cyro products the program is still useful as most acrylic sheets have similar tolerances. For tanks with Wave Boxes I generally like to go one size above what is recommended by Cyro's program.

Third, I would avoid solvent cements. Two part polymerizable cement, IPS Weld-on 40, should be used to cement parts together. Solvent joints are faster to prepare and dry which speeds up the fabrication process but they're not as strong. Look at IPS's website for product bulletins and compare the bonding strenghts. You'll notice Weld-on 40, a two part polymerized cement, is what is recomended for aquariums.

Good Luck!

First of all john tanks for your imput. Secondly when I imput my tank dimensions into the Cyro site it gives a recommendation of .672. The next larger size is .702 & the next one after that is .944. So according to your recommendations my tank should be made of cyro's .702(3/4" inch) material, and their .944(1") material if it were to have a wavebox? 1 inch material does seem excessive to me.

If anyone else has an opinion please chime in.

 

[ichthyman]

I know it seems excessive but unless someone can calculate the force generated by the waves, I'll continue to play it safe when it comes to installing an aquarium in someone else's house. I dislike litigation with insurance companies. I don't use Cyro because of the under sizing plus there are materials that machine nicer. Now, if this tank was going into my house I might be tempted to use Polycast's 3/4" material since it is truly 3/4". Also another construction technique for increased strength, would be to bend the front corners so there will be no seems. Reinforcements could then be hidden in the rear corners for extra strength. A 3/4" seem could easily be turned into 1.5" and not take away from the visual appeal of the aquarium.

 

[wbeavers]

Has Tunze GmbH come out with recomendations on acrylic tank construction with the wavebox. Please tell me if I'm wrong, but it seems that it is a product that has to be placed in a specially constucted tank. Without any guidelines someone can put this in any tank, and if it blows apart they can then press a civil suit. It seems to me that for your own protection you should issue, and distribute minimum tank construstion guide lines. I have seen 120gal tanks 4x2x2 made with 3/8(.375) material. This one I found easily:

http://www.premiumaquatics.com/ipiretail.htm

Far less than what the .672 the cyro site has recommended. According to John's recommendation it would have to be made of material exceeding 3/4" or twice that of some tanks of that size for proper wavebox safety.

 

[wbeavers]

Just to make this clear, I'm not bashing IPI or Premiuum Aquatics for selling a 3/8" 120. I think that it is sufficient for a standard use tank.

 

[rvitko]

You have to understand Acrylic practically doesn't exist in Germany. We specify in the manual aquariums built of glass according to Timeshenkos formula which specifies seam surface area for various size glass tanks. Acrylic is generally rare outside America because it is expensive, and it scratches easy and generally people are biased against plastic. Ithink it is mainly popular in America from earthquakes in California.

 

[ichthyman]

The problem is that acrylic sheet stretches more to accommodate the load than glass. Acrylic will keep stretching until either itââ"šÂ¬Ã¢"žÂ¢s or the ââ"šÂ¬Ã…"œglueââ"šÂ¬Ã¢"žÂ¢sââ"šÂ¬Ã‚ physical tolerance is exceeded. The ââ"šÂ¬Ã…"œglueââ"šÂ¬Ã‚ is weaker than the material. When under sized material is used the stress on the material and seams become greater. With material youââ"šÂ¬Ã¢"žÂ¢ll see crazing or ââ"šÂ¬Ã…"œstretch marksââ"šÂ¬Ã‚ at points farthest from the bow. With seams theyââ"šÂ¬Ã¢"žÂ¢ll begin to look ââ"šÂ¬Ã…"œmilkyââ"šÂ¬Ã‚ as they separate. Those 3/8" 120 tanks will hold, for how long is the question, but they WILL bow. The aquarium will look pregnant. Ã"šÃ‚½" material will deflect less at the height and length but 3/4" will bow minimally or not at all. The links provided back up everything Iââ"šÂ¬Ã¢"žÂ¢ve said. Those resources will allow you to make a more informed decision if you chose to heed the advice of the engineers who designed the products that will most likely be used in your new tank. Again, Iââ"šÂ¬Ã¢"žÂ¢ve separated fact from my opinions. Without knowing the energy released by the waves, I chose to recommend thicker material to hopefully cover my butt from litigation. I donââ"šÂ¬Ã¢"žÂ¢t agree that Tunze needs to make a acrylic tank construction guide as it is not their job to instruct other businessââ"šÂ¬Ã¢"žÂ¢ in their chosen craft. However, what I would like to see Tunze make some numbers available as to the kinetic energy transfer associated with this product.

 

[wbeavers]

I'm not asking Tunze USA to come out with a gude on how to construct a tank. I just want to see a minimum construction standard established. When a side blows out people will blame the wavebox not the tank. I just dont want Tunze USA getting hit with a class action suit in a couple years when these thin walled tanks start blowing out their sides. We have already established that the wavebox can't be dropped in just any tank. I think a set of guidelines are something that Tunze USA needs to have to protect themselves. There are standards for glass; Why not for acrylic? Do you also have a link to the Timeshenkos formula? Also I am looking into having this tank constructed of 3/4" material, and assembled with Weldon 40. I am just tankful that I asked the question, and had John & Rogers feedback. Thanks guys!

 

[ichthyman]

Also I am looking into having this tank constructed of 3/4" material, and assembled with Weldon 40.

Wise choice. Demand Polycast MG or Plexiglass G as they're both true to spec. and fabricates much nicer than the cheaper materials.

Do you also have a link to the Timeshenkos formula?

Roger sent told me where to look. http://www.saint-gobain-glass.com/fr/b1012.htm It is in German. I 've got someone working on the translation. If anything on the site is relevant to acylic I'll post it to this thread.

 

[wbeavers]

It was in French. Here is the translation I got.
http://translate.google.com/transla...&hl=en&ie=UTF-8&oe=UTF-8&prev=/language_tools

 

[ichthyman]

Dooh!:hmm4: :hammer: Thanks for the translation.

 

[wbeavers]

When I translated it fom German it didn't seem to work. I had assumed it would be in German also. I tried it a second time and had the same poor results. I was looking at the site and scratching my head when French words started jumping off the screen at me. So I know that "Doooo" feeling.

 

[rvitko]

Yes, St Gobain is a French company. If you just google Timoshenko's formula it is an engineering formula that is widely applied and it can be found in clear, well OK, extremely technical and difficult english.

 

[Acrylics]

wbeavers,

I think your fabricator is being a bit too cautious, insecure in his/her skills and/or materials, or maybe inexperienced with the waveboxes.

For starters, the 2" wide centerbrace must be wider. 4" would be better and 6" being optimal.

The tank *ought* to be built from 3/4" for two reasons; 1) the wavebox will apply repeated force to the tank walls and 2) the external overflow box will necessitate removal of structural materials where the back vertical panel meets the top panel.

Since no one that I know of has had these waveboxes in acrylic tanks over a prolonged period of time thus the effects over such time, it would be a wise choice to overbuild by at least one step just to be on the safe side.

As for Cyro's website and thickness calculators, well it has some <ahem> inaccuracies in it and a safety factor approximating 50% or so on tanks with tops and a deficiency of roughly 40% on tanks without tops for an equivalent deflection rate. This is not to say it isn't a good starting point however.

HTH?

James

 

[wbeavers]

Thanks James

 

[gwaco]

wbeavers , also one thing that has not been brought up and that is to make sure you overbuild your stand . i would be a shame to have your tank end up on the floor due to a poor stand . it needs to be rock solid ! that same wave motion will also be tranfered to the stand .

 

[wbeavers]

I win't have a problem with that. The stand has a shelf for a 48" viewable frag tank. Internal height is 42". This thing is way over built.